Everyone poops, but how often you do so could tell you a lot about your long-term health, according to a study published Tuesday in the journal Cell Reports Medicine.
A study of more than 1,400 healthy adults found that people who had infrequent bowel movements also showed signs of declining kidney function, while those who had much more frequent bowel movements than normal showed signs of liver problems.
“It’s well known that things like constipation are associated with chronic disease,” said Sean Gibbons, an associate professor at the Systems Biology Institute in Seattle and a co-author of the study.
It is less clear which comes first, constipation or chronic disease: does childhood constipation cause chronic disease in healthy people, or is constipation a consequence of chronic disease?
Gibbons and his team set out to answer that question using data from the now-defunct health and wellness company Arrivale. Study participants were healthy, mostly white adults living in the Pacific Northwest. The researchers analyzed blood and stool samples, BMI measurements, and questionnaire responses about diet, exercise habits, and mental health.
From blood samples, the team was able to detect chemicals in the blood that could indicate poor organ function, such as impaired kidney or liver function, and from stool samples they were able to sequence the genes of each person’s gut microbiome, providing a picture of the composition of beneficial and potentially harmful microbes that live there.
The researchers divided participants into groups based on bowel movement frequency: 1 to 2 bowel movements per week, 3 to 6 bowel movements per week, 1 to 3 bowel movements per day, and 4 or more bowel movements per day and diarrhea.
Research has found that the ideal number of bowel movements for optimal health is one or two times a day. Younger people, women, and people with lower BMIs tended to have fewer bowel movements. Chronic constipation (fewer than two bowel movements per week) was associated with decreased kidney function, while diarrhea (four or more times a day) was associated with decreased liver function.
Hungry microbes looking for food
Your intestines are filled with colonies of different microorganisms that feed on nutrients in your stool and ferment them. Their favorite food is fiber, but if stool stays in your intestines for too long (as in chronic constipation), the microorganisms run out of fiber. Instead, they turn to protein, which usually comes from the protein-rich mucus layer that lines the intestine.
“If we don’t feed the microbes, they’ll start eating us,” Gibbons says.
That creates three problems: When these microbes feed on protein, they produce toxic metabolic products, some of which have been linked to kidney and liver dysfunction. The more bacteria are forced to rely on protein-based foods, the more protein-loving bacteria there are and the fewer beneficial fiber-eating bacteria there are.
Recommendation
Eventually, microbes can begin to break down the mucous membrane in their search for food, making the gut “leaky,” allowing gut bacteria and metabolites that are toxic to other organs to leak into the bloodstream and cause inflammation that can lead to heart, liver and kidney disease, said Philip Hartman, PhD, an assistant professor of pediatric gastroenterology at the University of California, San Diego, who studies interactions between the gut microbiome and other organs.
“We can say with confidence that intestinal permeability at least contributes to disease,” said Hartman, who was not involved in the new study. “It may not be the only factor, but it often exacerbates the disease.”
A similar microbial sequence of events may occur in people with diarrhea, but in this case inflammation can cause deterioration of the mucous membrane lining the intestine, allowing toxins to enter the bloodstream.
“When you have diarrhea or constipation, you allow microbes to build up that produce toxins that contribute to disease,” said Joseph Petrosino, chair of molecular virology and microbiology at Baylor College of Medicine, who was not involved in the study.
The study found that people who regularly suffer from constipation or diarrhea have more protein-eating gut bacteria, while those who have one or two bowel movements a day have more bacteria that ferment dietary fiber.
Gibbons said it’s not clear why the study found that constipation was associated with kidney dysfunction and diarrhea was associated with liver dysfunction, but it may have to do with the fact that diarrhea makes it harder for the intestine to absorb bile acids (products of cholesterol metabolism), leaving more for the liver to process. The kidneys are more susceptible to metabolic products produced by protein-eating gut bacteria.
Because the study wasn’t a randomized clinical trial with an intervention, the new research can’t definitively conclude whether having more than one or two bowel movements per day is associated with chronic disease, but it seems possible that it is, Gibbons said.
“We hypothesized that people who have infrequent bowel movements or who are constipated would have more of these protein-based toxins in their blood, and that’s exactly what we found,” he says. “These toxins damage the liver and kidneys.”
Petrosino said that while you can’t necessarily control it, many lifestyle factors can help reduce both constipation and diarrhea.
“First and foremost, it’s important to eat a healthy diet and consume foods that promote the growth of good bacteria,” he said.
This includes eating plenty of fruits and vegetables and limiting alcohol and red meat. In the study, people who reported eating a diet high in fiber, drinking plenty of fluids, and exercising regularly tended to have healthier bowel movements. If you suffer from chronic conditions like upset stomach, constipation or diarrhea, probiotics could help, Petrosino said.
“There are probiotics out there that can help bring things back to normal, but if you’re already healthy, you probably shouldn’t take them,” he says. “You don’t need to fix what’s not broken.”
